Endoscopic instruments are widely known in which illumination of the field is provided by fiberoptic cables or bundles that transmit light through the barrel of the endoscope to its distal end and in which visual images are then transmitted back to the user through a series of lenses extending through the endoscope barrel from a field lens at the distal end to an eyepiece lens assembly at the endoscope's proximal end. Such endoscopes commonly include an outer tubular barrel, an inner barrel which houses a series of lenses for transmitting visual images through the endoscope, and fiberoptic cables or bundles positioned between the outer and inner barrels for transmitting light to the distal end of the endoscope and the adjacent field. See U.S. Pat. Nos. 5,046,816, 4,846,154, and 3,261,349. While such constructions provide sufficient illumination to the field in many instances, it has been found that such constructions do not provide adequate illumination to the field in some applications due to the limited quantity of fiberoptic cables or bundles which can be interposed between the outer and inner barrels without expanding the endoscope's diameter. This is particularly true in endoscopes which require greater illumination such as endoscopes having two field lenses for stereoscopic viewing or a first forwardly-directed field lens and a second laterally-directed field lens as disclosed in U.S. Pat. No. 4,846,154.
Attempting to include additional fiberoptic cables or bundles between the outer and inner barrels of such constructions is unrealistic because of diameter constraints as well as manufacturing cost and complexity. For example, it has been found that attempting to position large numbers of fiberoptic cables or bundles around an inner barrel while slipping an outer barrel over the fibers is exceedingly difficult to achieve without dislodging, damaging or otherwise misaligning the individual fiberoptic cables or strands.
An important aspect of this invention therefore lies in providing a relatively uncomplicated and efficiently manufacturable endoscope which provides ample illumination to the surgical or diagnostic field for endoscope's with one or more field lenses. Such results are achieved by eliminating the outer barrel from the endoscope and providing the endoscope with an outer casing around the inner barrel which is composed almost entirely of fiberoptic bundles. The fiberoptic bundles are interwoven together to form a braided sheath and a bonding means in the form of a curable embedding medium interlocks the bundles together and provides a relatively smooth outwardly-facing surface for the endoscope. Such a construction provides a greater number of fiberoptic cables in the endoscope than prior art devices without expanding the endoscope's diameter and provides ample illumination for endoscopes which may include more than one field lens. Such a construction also eliminates many of the manufacturing complexities encountered with prior art constructions.
In brief, the endoscope of this invention includes an elongated lens train having proximal and distal ends with an eyepiece lens assembly at its proximal end and at least one field lens at its distal end. The lens train includes objective and relay lens means for producing images and transmitting the same from the field lens or lenses back to the eyepiece lens assembly. An outer casing surrounds the lens train and includes a woven cylindrical sheath composed of a multiplicity of interlaced spirally-extending fiberoptic bundles or strands and a bonding means for maintaining the fiberoptic bundles in their configuration. The bonding means may take the form of a curable embedding medium composed of any of a number of well-known epoxy resins or other resins capable of being applied in liquid form and curing into a hardened state.
In a preferred form, the braided sheath includes a first spiral arrangement of a plurality of parallel fiberoptic bundles which are interwoven with an oppositely orientated, second spiral arrangement of a plurality of parallel fiberoptic bundles to form the braided tubular sheath. The proximal end of the sheath extends transversely outward from the inner barrel and forms a light-receiving post for receiving light from an external source and transmitting that light through the individual fiberoptic cables to their distal ends at the other end of the sheath. Those distal ends are exposed and surround the periphery of the field lens or lenses so that light transmitted therethrough illuminates the adjacent field.
Forming the outer casing of the endoscope from woven or interlaced spirally-extending fiberoptic bundles not only provides ample illumination of the field but is also advantageous in that the braided or woven structure imparts limited flexibility to the endoscope's barrel which is desirable in many applications. The spiral arrangement and opposite orientation of the two sets of fiberoptic bundles is also advantageous in that their distal ends terminate at angles to the barrel's longitudinal axis and provide improved light dispersion at the barrel's distal end and to the adjacent field.
Forming the endoscope's outer casing from the braided sheath also allows for efficient assembly of the endoscope. First, the braided or woven sheath is pre-assembled by interweaving together a plurality of fiberoptic bundles, each bundle including a plurality of individual fiberoptic cables. Preferably, the bundles are woven into a first spiral arrangement of a plurality of parallel fiberoptic bundles and a second similar, but oppositely oriented, spiral arrangement of fiberoptic bundles. The fiberoptic bundles may be woven together by known weaving methods commonly employed to form metal wire braided sheaths for coaxial cable or other known methods in the tubular textile manufacturing industry. The proximal end of the braided sheath is then formed into a light-receiving post that departs from the lens train and extends transversely thereto for connection to an external light source.
Once the tubular sheath is so formed, the sheath's diameter is expanded by pressing the distal and proximal ends together and the lens train is then inserted into the sheath. The lens train includes objective and relay lens means for transmitting images through the lens train and the proximal end of the lens train projects through an opening in the braided sheath for later connection to the eyepiece lens assembly. Thereafter the proximal and distal ends of the sheath are pulled apart to contract the sheath's diameter around the inner barrel so that the distal end of the sheath projects beyond a distal end of the inner barrel as well as the at least one field lens. Bonding means are then applied to the sheath for interlocking the fiberoptic bundles together and such bonding means may include a curable embedding medium composed of a well-known epoxy resin or other resin capable of being applied to the bundles in liquid form and then hardened or cured so that the endoscope barrel has a relatively smooth outwardly-facing surface. The distal end of the sheath is then severed around the periphery of the field lens or lenses to expose the distal ends of the individual fiberoptic cables. The exposed distal ends are then polished with an emery cloth or the like to allow transmission of light therethrough. The inner barrel is then connected at its proximal end to an eyepiece lens assembly and the light-receiving post is connected to an external light source for completing the endoscope.
In an alternate embodiment, the outer casing is formed from a plurality of elongated radial segments which are secured together by a bonding means to form the outer casing of the endoscope. Each of the segments includes a plurality of interlaced spirally-extending fiberoptic cables which are securely interlocked together by a bonding means such as a curable embedding medium. Such a construction is advantageous in that the embedding medium secures the segments to the lens train to prevent fluid ingress between the lens train and the outer casing.
Other advantages, features, and objects of the invention will become apparent from the specification and drawings.